Here are my thoughts on the topic.
Dairy good is not only milk, but also the following milk products: sour milk products (like yougurt, kefir, katik, buttermilk, etc.), cheese, etc. These products can contain less lactose than in the milk solids (due to fermentation during processing). It is also common for some of these products to contain living lactase-active bacteria, that can digest lactose.
Regular intake of these products can lead to certain changes in our small intestine microflora, so that the lacking lactase activity is substituted by the bacteria and thereby the tolerance grows. Maybe this is the intend of the Chinese government? Maybe they encourage the intake of sour milk products and not solid milk?
It is known, for example, that children with congenital/primary enzymatic deficiency develop the tolerance at the age of 6-10 years so that no special diet is needed anymore. This is true at least for such common enzymatic deficiencies like phenylketonuria and coeliacia.
In Russia, where I got my medical degree, it is common to use bacteria in the treatment of many types of primary intolerance combining this treatment with dietary support.